Metal-cutting apparatus

ABSTRACT

A metal-cutting apparatus, e.g., for the trimming of cast bodies of iron, steel, light metals and heavy metals, wherein a workpiece-support table is shiftable generally horizontally beneath a blade-carrying arm which is swingable in a vertical plane about a pivot axis. The pivot is mounted upon a carriage shiftable horizontally but perpendicular to the direction of movement of the table. Both the table and the carriage are provided with fluid-responsive stressing means for fixing the carriage and the table against play during the cutting operation.

I United States Patent 1 1 1111 3,709,096

Stender-Robertz 1 1 Jan. 9, 1973 UNITED STATES PATENTS [75] Inventor: Jost Stender-Robertz, Herzher [Ham Germany 3,577,828 5/1971 St1ckney ..90/l5 g 3,293,990 12/1966 Deflandre ..90/58 2,432,058 12/1947 Wiken et a1. ..90/D1G. 21 Assignee; Universal Maschinenq AP- 2,982,056 5/1961 Edquist ..51/99X paratebau u. Co. KG, Herz Baldlllg 1-1 berg] Germany Primary Examiner-Gi1 Weidenfeld Att0meyKar1 F. Ross [22] Filed: June 30, 1970 [57] ABSTRACT PP 51,107 A metal-cutting apparatus, e.g., for the trimming of cast bodies of iron, steel, light metals and heavy metals, wherein a workpiece-support table is shiftable [30] Forelgn Apphcanon Priority Data generally horizontally beneath a blade-carrying arm July 2,1969 Germany ..P 69 26 120.7 which is Swingable in a vertical Plane about a Pivot axis. The pivot is mounted upon a carriage shiftable 52 U.S.Cl. ..90/15 90/17 90/21.5 hmimmany but Perpendiculaf the directim 96/1316 51/99 movement of the table. Both the table and the car- [51] Int Cl 323C 3/14 riage are provided with fluid-responsive stressing means for fixing the carriage and the table against play [58] Field of Search.90/15, 17, 21.5, 56, 58, DIG.21, during the cutting operation 90/11 R; 51/99, 33 R, 34 R,92 R

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Attorney METAL-CUTTING APPARATUS FIELD OF THE INVENTION My present invention relates to metal-cutting apparatus and, more particularly, to an apparatus for trimming superfluous metal from castings or the like, e.g., of steel or iron, light metals such as aluminum and heavy metals such as die-cast zinc.

BACKGROUND OF THE INVENTION In the formation of metal bodies by casting, e.g. the casting of molten metal into molds under gravity or the distribution of fluid metals into a mold under external pressure or by centrifugal force, the cast bodies frequently are left with superfluous metal which must be trimmed. Superfluous metal includes deadheads (i.e., the metal filling the risers and sprues or vents or a mold), metal which is provided to permit trimming to a precise size or configuration, and metal elements or ligatures contained in cluster-cast bodies and the like.

It has been proposed heretofore to provide an apparatus for the trimming of a metal body, i.e., for the severing of metallic structures or excess metal from metal castings, which has a table upon which the body may be placed and a blade-support assembly which cooperates with the table to sever the excess metal from the body. The blades used for this purpose may be analogous to sawblades, i.e., may have well-defined teeth similar to those of a milling cutter, or may be abrasive (e.g., diamond particle) disks with which material is removed with abrasive techniques. The term cutting disk is used therefore to refer to both cutting blades of the tooth-type and abrasive-type cutting disks in which abrasive particles are bonded at least along the periphery of the disk.

In prior-art apparatus for this purpose, difficulties have been encountered which investigations have traced to excessive play in the parts supporting the cutting disk with respect to the workpiece. In general, such play results in a vibration of the blade support and of the blade itself and/or insecure positioning of the workpiece.

OBJECTS OF THE INVENTION It is, therefore, the principal object of the present invention to provide an improved system for severing excess metal from castings or other metal bodies using cutoff or like blades.

Another object of the invention is to provide an apparatus of the class described with means limiting the effect of play and vibration and, therefore, reducing or obviating the disadvantages mentioned above.

Still another object of this invention is to provide an improved apparatus for the removal of superfluous material from metal castings which is more versatile and of simpler construction than earlier apparatus for the same purpose.

SUMMARY OF THE INVENTION These objects and others which will become apparent hereinafter, are attained, in accordance with the present invention, with an apparatus which comprises a support structure, a workpiece carriage shiftable on this support structure, preferably in a horizontal plane and with respect to horizontally disposed guide surfaces, and a blade-carrying carriage slidably mounted on the support structure for movement perpendicular to the movement of the workpiece carriage but also in a horizontal plane and with respect to a horizontally disposed guide surface. The blade-carrying carriage, according to this invention, comprises a pivot (generally horizontal and parallel to the direction of movement of the workpiece and perpendicular to the direction of movement of the blade carriage) about which a blade-support arm is swingable; the latter arm overhang the workpiece support and is provided at its free end with a rotating blade lying in a plane parallel to the swing plane of the arm and perpendicular to the direction of displacement of the workpiece.

According to an essential feature of this invention, the play of the apparatus is taken up by at least one fluid-responsive stressing means interposed between one of the carriages and the respective guide surface and energizable during the severing operation to prevent play between this carriage and the support structure. 1

According to a more specific feature of the invention, the play-eliminating, fluid-responsive means for stressing the carriage against the support structure, comprises a guide channel in the carriage which is juxtaposed with the horizontal drive surface or ways of the support structure and is provided with a hydraulic cylinder whose piston or plunger is urged against the ways upon pressurization of the cylinder. To this end, the guide channel, in which the ways or guide members are received, may be undercut so that upon pressurization of the hydraulic cylinder, edges, ridges or other abutment surfaces of the carriage, oppose the cylinder arrangements, and are brought into tight contact with the guide surfaces. Preferably, the play-absorbing or eliminating means is provided at least for the workpiece carriage.

Another feature of this invention resides in the provision of a similar hydraulically 'pressurizable means for taking up the play of the arm-carrying carriage. As previously noted, the arm carriage is shiftable horizontally in a direction perpendicular to the workpiece-support table or carriage and, therefore, parallel to the plane in which the arm is swingable. The arm carriage may be provided with horizontal bores, preferably a pair of horizontally-spaced bores, lying in a horizontal plane perpendicular to the vertical plane of arm swing and equispaced on opposite sides of this vertical plane, the bores slidably receiving a pair of shafts or bars, of circular cross-section, constituting the ways or guide surfaces of the support structure along which the arm carriage is displaceable. In this case, a pair of hydraulic cylinders is provided in the arm carriage on diametrically opposite sides of each of the shafts and are formed with pistons or plungers adapted to bear symmetrically thereon simultaneously to take up any play between these carriages and the support structure.

Advantageously, the workpiece-support table or carriage is provided with a workpiece holder orientatable about both a vertical axis, i.e., an axis parallel to the plane of swing of the blade arm and transverse to the direction of displacement of the workpiece table, and about a horizontal axis perpendicular to this vertical axis and lying either parallel to the direction of displacement of the workpiece table or transversely thereto. It has been found that, when the apparatus as previously described is used primarily for the removal of the deadheads and other superfluous metal members of a casting, such freedom of orientation is essential because of the great variety of configurations of the castings which must be handled. The means and controls for displacing the movable portions of the holder should be disposed to either side of the blade position or upon the side of the holder remote from the blade carriage, thereby allowing accessability to all of the controls which may require adjustment. Furthermore, it has been found desirable to provide, upon the same movable workpiece carriage, or on the same ways, two or more workpiece holders which may be operated or positioned individually so that, during cutting with one holder, the other holder may be used to mount a workpiece and vice versa.

An important feature of this invention resides also in the control of the blade arm and its construction. The blade, as already noted, lies in a vertical plane perpendicular to the pivot axis of the arm and is journaled at the free end of the latter. It has been found to be advantageous, especially when cuts are required through large cross-sections, to impart an oscillation to the blade-carrying arm in the longitudinal direction of the latter, i.e. radially with respect to the blade. This is effected in the system of the present invention by mounting the arm pivot in a horizontally reciprocatable bearing block and hydraulically or pneumatically displacing this block at a relatively high frequency (e.g. 60 cycles per sec to kc per sec). The fluid-responsive oscillating device may include a double-acting pressurizable cylinder, the opposite sides of which are pressurized through a reversible valve, or a single-acting cylinder working against a spring. The control means may include a motor for oscillating the valve or any other reciprocating system conventional in the art.

The cutting movement of the arm is, of course, the swinging movement about its pivot axis and there is provided, in accordance with the present invention, a hydraulic cylinder which is pivotally mounted upon the blade carriage and is coupled with the arm for swinging the latter. The arm is preferably also provided with a rearward extension, i.e. an extension in the direction away from the blade, which is provided with a counterweighting body, e.g., the drive motor for the blade. The drive motor may be connected with the blade via a V- belt transmission and it has been found to be advantageous to provide means, e.g., telescoping parts or the like, for tensioning the V-belt or, in more general terms, adjusting the distance between the motor and the blade pulley. Between the blade disk and the support arm there is advantageously provided a control panel or switching arrangement enabling convenient regulation of all of the functions of the apparatus.

DESCRIPTION OF THE DRAWING The above and other objects, features and advantages of the present invention will become more readily apparent from the following description, reference being made to the accompanying drawing in which:

FIG. 1 is a side-elevational view, partly in diagrammatic form, of an apparatus for the removal of deadheads and like superfluous metal structures from castings of various configurations in accordance with the present invention;

FIG. 2 is a diagram illustrating the means for hydraulically pressurizing the play-limiting means of the machine of FIG. 1;

FIG. 2A is a view generally along the line IIA IIA of FIG. 2;

FIG. 2B is a view generally in the direction of the arrow IIB of FIG. 2;

FIG. 3 is a side-elevational view, partly broken away, of a less diagrammatic representation of a machine in accordance with the present invention, partly broken away and partly in diagrammatic form;

FIG. 4 is a front view of the machine of FIG. 3;

FIG. 5 is a detail view, partly in cross-section, illustrating the arm-oscillating means in accordance with the present invention; and

FIG. 6 is a detail view, partly in diagrammatic form and with parts broken away to illustrate the means for adjusting the position of the motor in accordance with the present invention.

SPECIFIC DESCRIPTION As illustrated diagrammatically in FIG. 1, an apparatus for the severing of deadheads and like superfluous parts from castings of steel, iron, light metals and heavy metals comprises a support structure 1 which may be mounted by a pedestal 1a and bolt holes lb upon any bench or table, in accordance with conventional practices. The support structure basically comprises a horizontal guideway 10, shown in end view in FIG. 1 and oriented upwardly in FIG. 2, upon which the workpiece-support table 5 is horizontally shiftable, i.e. movable perpendicular to the plane of the table in FIG. 1. Above the table, upon a blade carriage 2, there is mounted a blade-support arm 3. In the embodiment of FIG. I, the arm 3 comprises a pair of arm members 30 and 3b, rigidly interconnected and forming an obtuse angle with one another; arm member 3b is pivotally mounted between the upstanding arms of the carriage 2, the latter having an upwardly open U-shaped configuration (see FIG. 2A).

At the free end of arm 3a, there is journaled a cutoff disk (blade) 4 which is partly enclosed by a head 30, carried by the arm 3a, and shielding the operator against sparks and chips which may be cast off from the cutting zone.

A console 3d is also carried by the arm and is provided with switching devices necessary for control of the apparatus. Since, apart from the hydraulic means for restricting the play of the moving parts, the control means is not part of the invention and is conventional,

it will be not discussed in detail.

As illustrated in FIG. I, the blade 4 is provided with V-belt pulleys which are connected by V-belts enclosed within a shield 3e with the driven pulleys of a motor 3f ment of the arm 3a, 3b about its pivot axis 2b in a plane parallel to the plane of the paper, there is provided a hydraulic arrangement 3m consisting of a hydraulic cylinder 3n pivotally connected at its lower end to the carriage 2 and receiving a piston 3p pivotally connected at its upper end 3q to the arm 3b. Hence, excursion of the piston 3p swings the arm 3a, 3b in the counterclockwise sense to lower the blade 4, while retraction of the piston 3p swings the arm 3a, 3b in the clockwise sense to lift the blade 4 out of engagement with the workpiece. The workpiece holders which are mounted upon the table 5, may be identical to those of FIGS. 3 and 4.

According to an important feature of this invention, the worktable 5 is provided with a hydraulic cylinder 6 (FIGS. 2 and 2B) whose piston 7 carries a stressing disk 8 received in an undercut slot 9 of the guide ways of the machine structure 1. The undercut slot 9 runs the entire displaceable length of the table 5 and has a pair of ledges 9a and 9b overhanging the disk 8. When the cylinder 6 is hydraulically pressurized, therefore, the disk 8 is drawn outwardly against theledges 9a and 9b and the surface 5a of the table is locked against the surface lc of the guideways, thereby precluding any play whatsoever.

The cylinder 6 is connected via line 14 of the hydraulic network N actuating the apparatus. For example, the network N may include a pump P drawing the hydraulic fluid from a reservoir R and passing it through a valve V to the hydraulic cylinder C whose piston C is connected with the carriage 5 to displace the latter when the valve V is in the broken line position illustrated In the broken-line position of the valve, hydraulic fluid flows from the pump P to the cylinder C to displace the workpiece carriage 5 while the cylinder 6 is connected with the reservoir R to relieve the stress between the disk 8 and the ledges 9a and 9b. When, however, the table 5 rises to the desired position, the valve V via the handle H, is shifted into its solid-line position, thereby terminating displacement of the cylinders 16 but locking the carriage 5 by pressurization of the cylinder 6.

Similarly, the carriage 2 is provided with a base 10 for the blade arm 3, the slide 10 having cylindrical bores 10a and 10b in which a pair of parallel shafts III are receivable. In this arrangement, the shafts 11 constitute the guide ways for the carriage 2, 10. The carriage is provided with a pair of diametrically opposite cylinder 13 on opposite sides of each shaft 11, slidably receiving pistons 12 which are urged like the pads of a disk brake against the shafts 11 to lock the slideable carriage 2, 10 against play with respect to the shafts after the cylinder C, is operated to displace the blade carriage. To this end, a valve V, is provided with a lever H, and can be operated to relieve the cylinders 13 when the cylinder C, for displacement of the slide 2, 10 is desired. In the alternate position of the valve, the cylinder C, is relieved and the cylinders 13 are pressurized to lock the assembly. The valves V and V, have been shown in simplified form, it being understood that a conventional distributing and three-way valve arrangement may be provided, if it is desired to provide double-acting cylinders at C and C,. The means for displacing the carriages is not, however, a part of the present invention, it being merely noted that the hydraulic device for displacing the carriages may be coupled with the play-eliminating hydraulic stressing devices.

As soon as the worktable is laterally shifted to its desired position, therefore, the stressing disk 8 is brought into play to lock the table to the machine structure 1 against play. Similarly, during displacement of the blade carriage 2, 10 the cylinders 13 are relieved. Also the pistons 12 are brought into operation when the carriage 2, 10 is placed in proper position for cutting. Consequently, both the worktable and the arm carriage are fixed without delay in the cutting position.

In FIGS. 3 and 4, I have shown an apparatus which, while generally similar to that described with respect to FIG. 1 and 2, differs in some details. In this embodiment, which is preferred to the system of FIG. 1, the machine structure 16 forms a pair of horizontal guide rails 17, generally similar to the rails 11, which are held in place between a pair of brackets 16a. The carriage 18, which is shiftable along these rails, is moved horizontally by a cam 16b rotatably mounted in the housing structure 16 in a manner not further illustrated and displaced by a hand-wheel arrangement as represented at 160. As the cam 16b swings to the left, therefore, the carriage 18 is shifted correspondingly. A coupling may be provided between the cam 16b and the carriage 18 to ensure displacement of the assembly in the opposite direction.

The carriage 18 forms a journal for a swingable arm 19, the free end of which is provided with the cutoffdisk 20. The arm 19 is pivotally mounted on the carriage 18 at 21 for swinging movement about the horizontal axis defined by this pivot.

The arm 19 is extended rearwardly at 22. To this end, the arm 19 is integral with a tubular member 22a at a base 22b which is surrounded on the pivot 21 and includes an obtuse angle with the arm 19. The tubular member 22a opens rearwardly and telescopingly receives a toothed stud 22c carrying the pedestal 22d of the drive motor 23. A locking collar 222 may be removed to permit axial adjustment of the stud 22c between, for example, its solid-line position and its dotdash line position as shown in FIG. 6, thereby tightening the belts. Thereafter, the collar 22e is replaced to lock the elongatable assembly 22 in its new position.

Referring again to-FIG. 3, it will be apparent that the motor 23 is provided with V-belt pulleys 24a which are connected by V-belts 24 with the driven pulleys 24b of the blade 20, the V-belt drive being received in a safety shield or housing 240. Between the slide or carriage 18 and the rearward extension of the blade-carrying arm 19, there is provided a hydraulic cylinder 25 which, when extended, swings the arm 19 in the counterclockwise sense (FIG. 3). I

As illustrated in FIG. 5, the pivot shaft 21 is mounted in a block 21a which is horizontally slidable in a guide opening 22b formed in the upright portions on each side of the carriage 18. An arm 26 at each end of the pivot shaft 21 is provided on each of the blocks 21a and is connected via a piston rod 27a with a piston 27 slidable in a hydraulic cylinder 28. A reversing valve 28a may be provided with the plunger 28b reciprocated by the cam 280 of a motor 28d to alternately pressurize opposite sides of the cylinder and thereby reciprocate the piston 27 and vibrate the block 21a, the arm 19 and the blade 20 in the longitudinal direction of the arm 19 for the reason previously described. In place of the double-acting cylinder 28, a single-acting system may be provided, in which case a spring 29 bears upon the piston 27 in one direction; only the opposite side of the cylinder is intermittently charged with fluid under pressure and drained.

From FIG. 4, it will be apparent that the workpiece table of the embodiment of FIGS. 3 and 4 is supported on a pair of guide rails 30 extending horizontally but defining a plane inclined to the horizontal (see FIG. 3). Each of the workpiece carriages 31 of this embodiment is provided with hydraulic means for stressing the carriage against the guide way as described in connection with FIG. 2. The carriage 31 comprises a pair of workpiece holders generally represented at 33 and including a vise as indicated at 36. The holders comprise generally horizontal platforms (see member 33 in FIG. 3). Upon this table, there is mounted conventional means for positioning the vise 36 and for swinging this vise about the horizontal axis 34, parallel to the rails 30 and about a vertical axis 32 in the cutting plane. The means for swinging the vise 36 about the horizontal axis 34 can include a handwheel 34a for driving a cradle or rocker 35 and a locking member 34b for positioning the assembly and retain its position in the usual manner. The cradle 35 thus supports the ball-bearingmounted jaws of the vise which can be brought together or spread by a crank 36a. Similar means may be provided to permit displacement of the vise about the vertical axis. A switch panel or console 37 is provided on the swingable arm 19 between the disk 20 and the pulley 2412 (see FIGS. 3 and 4) and carries both the electrical and hydraulic controls of the apparatus. The system of FIGS. 3 6, of course, is operated in a manner analogous to that of FIGS. 1 and 2.

The improvement described and illustrated is believed to admit of many modifications within the ability of persons skilled in the art, all such modifications being considered within the spirit and scope of the invention except as limited by the appended claims.

I claim:

1. An apparatus for severing excess metal from a cast or other metal body, comprising:

a support structure formed with first horizontal guide means and second horizontal guide means perpendicular to said first guide means;

a workpiece-support carriage on said first guide means linearly displaceable along said support structure generally horizontally;

means for linearly displacing said workpiece carriage on said support structure;

a blade-carrying arm shiftably mounted for displacement in a vertical plane generally perpendicular to the direction of displacement of said workpiecesupport carriage; a blade carriage mounting said arm and linearly displaceable on said second guide means in said plane relative to said support structure;

means for linearly displacing said blade carriage along said second guide means; and stressing means between at least one of said carriages and said support structure and effective in a cutting position of said one of said carriages for locking the respective carriage against said support structure to exclude play therebetween, said support structure including a shaft forming a guide rail for said one of said carriages and said one of said carriages is provided with a bore slidably receiving said shaft, said stressing means including a pair of diametrically opposite hydraulic cylinders formed in said one of said carriage and opening in the direction of said shaft, and respective pistons received in said cylinders and bearing upon said shaft in opposite directions upon hydraulic pressurization of said cylinders.

2. The apparatus defined in claim 1 wherein said one of said carriages is said workpiece-support carriage.

3. The apparatus defined in claim 1 wherein one of said carriages is said blade carriage.

4. The apparatus defined in claim 1 wherein said workpiece-support carriage is provided with a workpiece holder displa'ceable about a vertical axis and a horizontal axis to orient a workpiece with respect to a blade carried by said arm.

5. An apparatus for severing excess metal from a cast or other metal body, comprising: i

a support structure formed with first horizontal guide means and second horizontal guide means perpendicular to said first guide means;

a workpiece carriage on said first guide means linearly displaceable along said support structure generally horizontally;

means for linearly displacing said workpiece carriage on said support structure;

a blade-carrying arm shiftably mounted for displacement in a vertical plane generally perpendicular to the direction of displacement of said workpiece carriage; a blade carriage mounting said arm and linearly displaceable on said second guide means in said plane relative to said support structure;

means for linearly displacing said blade carriage along said second guide means;

stressing means between at least one of said carriages and said support structure and effective in a cutting position of said one of saidcarriages for locking the respective carriage against said support structure to exclude play therebetween, said stressing means including a hydraulic cylinder on said one of said carriages and a piston hydraulically displaceable in said cylinder and bearing against the respective guide means of said support structure upon pressurization of said cylinder to lock said one of said carriages against said support structure;

pivot means mounting said arm upon said blade carriage for swinging movement about a horizontal axis perpendicular to said plane, said arm having a free end overhanging said workpiece-support carriage and provided with a blade lying in said plane, and a motor mounted on said arm and coupled with said blade; and

means for longitudinally oscillating said arm during the cutting of a workpiece.

6. The apparatus defined in claim 5, further comprising means enabling shifting of said pivot means generally in said longitudinal direction relative to said blade carriage, said means for oscillating said arm including a hydraulic cylinder coupled with said pivot means.

ing means mounting said motor uponsaid extension at an adjustable distance from said blade.

9. The apparatus defined in claim 5, further comprising a control panel for said motor mounted on said end of said arm. 

1. An apparatus for severing excess metal from a cast or other metal body, comprising: a support structure formed with first horizontal guide means and second horizontal guide means perpendicular to said first guide means; a workpiece-support carrIage on said first guide means linearly displaceable along said support structure generally horizontally; means for linearly displacing said workpiece carriage on said support structure; a blade-carrying arm shiftably mounted for displacement in a vertical plane generally perpendicular to the direction of displacement of said workpiece-support carriage; a blade carriage mounting said arm and linearly displaceable on said second guide means in said plane relative to said support structure; means for linearly displacing said blade carriage along said second guide means; and stressing means between at least one of said carriages and said support structure and effective in a cutting position of said one of said carriages for locking the respective carriage against said support structure to exclude play therebetween, said support structure including a shaft forming a guide rail for said one of said carriages and said one of said carriages is provided with a bore slidably receiving said shaft, said stressing means including a pair of diametrically opposite hydraulic cylinders formed in said one of said carriage and opening in the direction of said shaft, and respective pistons received in said cylinders and bearing upon said shaft in opposite directions upon hydraulic pressurization of said cylinders.
 2. The apparatus defined in claim 1 wherein said one of said carriages is said workpiece-support carriage.
 3. The apparatus defined in claim 1 wherein one of said carriages is said blade carriage.
 4. The apparatus defined in claim 1 wherein said workpiece-support carriage is provided with a workpiece holder displaceable about a vertical axis and a horizontal axis to orient a workpiece with respect to a blade carried by said arm.
 5. An apparatus for severing excess metal from a cast or other metal body, comprising: a support structure formed with first horizontal guide means and second horizontal guide means perpendicular to said first guide means; a workpiece carriage on said first guide means linearly displaceable along said support structure generally horizontally; means for linearly displacing said workpiece carriage on said support structure; a blade-carrying arm shiftably mounted for displacement in a vertical plane generally perpendicular to the direction of displacement of said workpiece carriage; a blade carriage mounting said arm and linearly displaceable on said second guide means in said plane relative to said support structure; means for linearly displacing said blade carriage along said second guide means; stressing means between at least one of said carriages and said support structure and effective in a cutting position of said one of said carriages for locking the respective carriage against said support structure to exclude play therebetween, said stressing means including a hydraulic cylinder on said one of said carriages and a piston hydraulically displaceable in said cylinder and bearing against the respective guide means of said support structure upon pressurization of said cylinder to lock said one of said carriages against said support structure; pivot means mounting said arm upon said blade carriage for swinging movement about a horizontal axis perpendicular to said plane, said arm having a free end overhanging said workpiece-support carriage and provided with a blade lying in said plane, and a motor mounted on said arm and coupled with said blade; and means for longitudinally oscillating said arm during the cutting of a workpiece.
 6. The apparatus defined in claim 5, further comprising means enabling shifting of said pivot means generally in said longitudinal direction relative to said blade carriage, said means for oscillating said arm including a hydraulic cylinder coupled with said pivot means.
 7. The apparatus defined in claim 5 wherein said arm extends beyond said pivot means away from said workpiece-support carriage, further comprising a hydraulic cylinder coupled with the extension of saId arm for positioning same.
 8. The apparatus defined in claim 7, further comprising means mounting said motor upon said extension at an adjustable distance from said blade.
 9. The apparatus defined in claim 5, further comprising a control panel for said motor mounted on said end of said arm. 